This invention relates to a combinatorial weighing method and apparatus wherein a plurality of weighing machines are supplied with articles, items of weight data from the weighing machines are combined, weighing machines are selected to give a combination of weight data within preset allowable limits and satisfying a predetermined condition, and the articles are discharged from the selected weighing machines.
The combinatorial weighing method includes steps of forming combinations of the weight data obtained from the plural weighing machines, taking the sum of each combination to give a combined weight value, and obtaining the combination of weighing machines which gives a combined weight value that is within preset allowable limits and equal or closest to a target value. In general, with such an arrangement, the larger the number of combinations, the greater the accuracy that can be obtained. When a number of weighing machines produce outputs of identical weight data there is a decrease in the number of combinations within the preset allowable limits and, hence, a decline in measurement accuracy. At times, the only combinations that can be obtained are those that give a combined weight value outside of the allowable limits. Such a weight value will hereafter be referred to as an "unsatisfactory" combined weight value.
It is obvious that the occurrence of unsatisfactory combined weight values is an undesirable phenomenon in a combinatorial weighing system. Conventionally, the occurrence of unsatisfactory weight values has been prevented by not discharging the articles from the weighing machines when not a single combined weight value from all combinations of the weight data falls within the allowable limits. Then, some of the weighing machines are supplied with additional articles and a combinatorial weighing is again performed to obtain new combined weight values from the combinations that will be obtained.
With the foregoing method, however, the efficiency of the processing performed by the combinatorial weighing apparatus declines in proportion to the number of weighing cycles in which articles are not discharged. In addition, the fact that some weighing machines are supplied with additional articles following a non-discharge cycle frequently results in an "overscale" phenomenon, in which an excess of the articles is delivered.